Metformin Treatment During Pregnancy And Its Effect On Fetal Growth: A Literature Review

The prevalence of pregnant women with gestational diabetes mellitus or type 2 diabetes has increased in the last two decades. This has led to a higher frequency of maternal and fetal complications associated with this comorbidity that could put at vital risk the mother and the fetus. The treatment of choice for this pathology in pregnancy is insulin, due to its lack of significant transplacental passage and safety in pregnancy confirmed by the long history of use.A few randomised controlled trials have investigated metformin, a biguanide that is used as first line of treatment for type 2 diabetes mellitus in case of nonpregnant patients, in the treatment of gestational diabetes, type 2 diabetes mellitus associated with pregnancy and for reducing the insulin resistance in obese pregnant patients and pregnant patients with polycystic ovary syndrome. Due to is the free transplacental passage, metformin could have effects of the fetal side, although the risk of teratogenicity is low. In this study, we analysed the effect of metformin on fetal growth and birth weight reported in 9 randomised controlled trials that were published in the past ten years. The nine randomised controlled trials included several 1574 pregnant women that took metformin treatment during pregnancy for gestational diabetes, type 2 diabetes and to reduce insulin resistance in the case of obese pregnant women and pregnant women with polycystic ovary syndrome. This study concludes that metformin has reduced or no effect on fetal growth and birth weight compared with standard insulin treatment in diabetes mellitus or placebo in the cases of pregnant women with obesity or previous polycystic ovary syndrome without diabetes.